Directly from the forum where the issue was first reported:
Heres an FOV hack for the demo:
http://dl.tocaedit.com/bioshockdFOV.zip
Reportedly not working on Vista 64bit...
I'll make one for the retail game when I get a hold of it.
Even though I have no use for it on my 4:3, I tested it just to make sure everyone over here can stop whining. It works great and regarding racer_s' track record, I'm sure a FOV hack for the full game will be out in no time (at least a lot sooner than any official patch).